RFID System With A Mobile RFID Reader

ABSTRACT

An RFID system includes a pair of guide tracks located on opposite boundaries of at least one zone. A channel is movably attached to the guide tracks and is configured to move along the guide tracks through the at least one zone. A mobile RFID reader is movably attached to the channel and the mobile RFID reader is paused at a plurality of read points to scan for RFID tags located. The read points are determined by an arrangement of a plurality of hexagonal areas which are grouped together to create a combined area, where the combined area is aligned with the predefined area to define locations of the plurality of hexagonal areas, and where substantially central locations of each hexagonal area represent the plurality of read points.

BACKGROUND

Radio Frequency Identification (RFID) technology uses radio frequency(RF) waves to exchange information for a variety of purposes, includingidentification. An RFID system typically includes an RFID reader ortransceiver having an antenna and an RFID tag or transponder containinginformation. Active RFID systems utilize a dedicated power source topower RFID tags. In contrast, passive RFID systems do not rely on aninternal power source to power RFID tags. Instead, the antenna of theRFID reader emits RF signals to activate passive RFID tags within areading range. When activated, the passive RFID tags are configured totransmit a responding signal to the RFID reader.

RFID technology has been widely used for tracking and monitoring items.For example, RFID systems are used in warehouses to monitor the movementof products and inventory. In many inventory control systems, an RFIDtag containing a unique code is attached to items in the warehouse. Thisallows each item in the warehouse to be identified by the unique code ofthe attached RFID tag. One or more RFID readers are installed atpredefined locations in the warehouse to read the RFID tags attached tothe items. By keeping track of all the unique codes read by the RFIDreaders, an accurate record of inventory levels and movement ismaintained. Accordingly, the use of RFID technology in inventory controlsystems also reduces the possibility of human error, which may arise inmanual tracking processes.

In large-scale deployment of RFID technology for inventory controlsystems, the positioning of the RFID readers in the warehouse iscrucial. Current positioning techniques of the RFID readers inwarehouses typically result in blind-spots in the RFID signal coverageor interferences between the RFID readers. For example, insufficientRFID readers or poor RFID reader placement in the warehouse may resultin less than 100% area coverage of the RFID reader signals. Therefore,RFID tags in certain locations of the warehouse will not be read by theRFID readers. Similarly, if the RFID readers are spaced too closelytogether, interference among the RFID readers reduces the reliabilityand efficiency of the RFID system.

It would thus be beneficial to have the ability to obtain data from RFIDtags positioned throughout a relatively large space without sufferingfrom the disadvantages and drawbacks associated with conventionaltracking techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of the present invention will become apparent to those skilledin the art from the following description with reference to the figures,in which:

FIG. 1 shows a simplified view of an RFID system, according to anembodiment of the invention;

FIG. 2 shows a simplified view of an RFID system and read points,according to another embodiment of the invention;

FIG. 3 shows a hexagonal area representing a circular reading range ofan RFID reader, according to an embodiment of the invention;

FIG. 4 shows a plurality of hexagonal areas arranged together to form ahoneycomb combined area, according to an embodiment of the invention;

FIG. 5A shows a first type of alignment of a predefined area and acombined area, according to an embodiment of the invention;

FIG. 5B shows a second type of alignment of a predefined area and acombined area, according to an embodiment of the invention;

FIG. 6 shows the first type of alignment of the predefined area beingmoved along a direction of the coinciding edges of the predefined areaand a hexagonal area, according to an embodiment of the invention;

FIG. 7 shows a close-up view of a predefined area being aligned with acombined area, according to an embodiment of the invention;

FIG. 8 shows an illustration of the number of hexagonal areas that areneeded (H_(fraction)) for different values of E_(fraction), according toan embodiment of the invention;

FIG. 9 shows combined area with a first and second zone, according to anembodiment of the invention;

FIG. 10 shows a minimum area enclosing rectangle (MAER) for a polygonalshape, according to an embodiment of the invention;

FIG. 11 shows a block diagram of a location optimizing unit fordetermining read points, according to an embodiment of the invention;

FIG. 12 shows an RFID system, according to another embodiment of theinvention;

FIG. 13 shows a block diagram of a reader manager, according to anembodiment of the invention;

FIG. 14 shows a block diagram of an RFID control system, according to anembodiment of the invention; and

FIG. 15 shows a flow diagram of a method for moving a mobile RFID readerwithin a zone to scan for RFID tags, according to an embodiment of theinvention.

DETAILED DESCRIPTION

For simplicity and illustrative purposes, the present invention isdescribed by referring mainly to an exemplary embodiment thereof. In thefollowing description, numerous specific details are set forth in orderto provide a thorough understanding of the present invention. It will beapparent however, to one of ordinary skill in the art, that the presentinvention may be practiced without limitation to these specific details.In other instances, well known methods and structures have not beendescribed in detail so as not to unnecessarily obscure the presentinvention.

Disclosed herein are systems and methods for moving an RFID readerwithin a predefined area to allow the RFID reader to scan for RFID tags.The predefined area may be any area where RFID tags are expected to belocated. For example, the predefined area may be at least a portion of awarehouse in which items having RFID tags are located.

According to an example, the predefined area is divided into zones. Theterm “zone,” as used herein, refers to a region within the predefinedarea that a single RFID reader may move through to read RFID tagslocated within and/or outside of the zone. For instance, the RFID readermay be moved to or near a boundary of the zone, yet may still beoperable to read RFID tags located outside of the zone. The zone may beany region within the predefined area or may be the entire predefinedarea itself. The zone may be a three-dimensional area having boundariesin the X, Y, and Z dimensions, as described in greater detail below. Insome embodiments, the predefined area may be divided into multiple zonesand one or more RFID readers may be configured to move through the oneor more zones, and scan for RFID tags located within the predefinedarea.

A pair of guide tracks between which one or more RFID readers may travelmay be placed on opposite edges of at least one of the zone boundaries.For example, if a zone is a rectangle having a length and a width, theguide tracks may be placed along edges of the width of the rectangle.However, the predefined area may have multiple zones and the guidetracks may be placed on the edge of a first zone and the opposite edgeof a second zone. The guide tracks may comprise any mechanical means ofsecuring a channel thereto to allow the channel to move along the guidetracks to traverse the zone. The term “channel,” as used herein, refersto a mechanical means of moving an RFID reader along the channel. Forexample, the guide tracks and the channel may comprise a rail, wheels,magnets, etc., on which the RFID reader is movably attached. Therefore,the RFID reader is operable to move along the channel while the channelis operable to move across the zone along the guide tracks. In thismanner, the RFID reader may be moved to any position within the zone toscan for RFID tags.

In an embodiment, the RFID reader may pause at optimized read pointswithin the zone. The term “pause,” as used herein, refers to a decreasein the speed of movement of the RFID reader. As the RFID reader movesalong the channel and/or the channel moves along the guide tracks, theRFID reader may be slowed down or stopped at the read points to allowthe RFID reader to scan for RFID tags. The RFID reader may remainsubstantially motionless at the read points for any reasonably suitableduration of time.

The optimized read points at which the RFID reader may be paused may bedetermined by tessellating the predefined area. That is, a plurality ofhexagonal areas may be arranged together to form a honeycomb grouping orcombined area, such that substantially no gaps exist between any twohexagonal areas. The combined hexagonal areas may be equal in size orlarger than the predefined area. The combined area of hexagonal areasmay be aligned with the predefined area. It should be understood thatthe predefined area does not have to be physically tessellated bymarking or otherwise altering the predefined area itself, but that thepredefined area need only be conceptually tessellated. In any regard,each of the hexagonal areas may represent an approximate reading rangeof an RFID reader. Therefore, the number of hexagonal areas needed tocover the predefined area is dependant upon the reading range of theRFID reader. The larger the reading range, the fewer the number ofhexagonal areas need to cover the predefined areas. The process oftessellating the predefined area and determining the read points isdiscussed in greater detail below.

The methods and systems described herein allow for the efficient readingof RFID tags located at different locations in a predefined area toachieve substantially 100% coverage of the predefined area. The systemsand methods may be used in any reasonably suitable RFID applications,including tracking and monitoring RFID-tagged items, such as inventoryin a warehouse. In addition, substantially optimized read points topause and read RFID tags, as opposed to continually moving the RFIDreader throughout the predefined area, may be determined, which limitsredundant reads of RFID tags. Moreover, determining specific optimizedread points also allows coverage of the entire predefined area with thesmallest possible number of reader pauses. This significantly improvesthe efficiency of the reading process as well as the reader utilization.

Moreover, the dynamic positioning and movement of the channel and theattached RFID reader allows for greater adaptation and provides greaterflexibility in the choice of readers. That is, many different RFIDreaders are available, which have different reading ranges. The systemsand methods described herein allow RFID readers with different readingranges to be interchanged, because the RFID readers may be moved todifferent read points within a zone of the predefined area to accountfor differences in reading range. For instance, if an RFID reader havinga different reading range is used, a new set of read points may bedetermined by re-tessellating the predefined area based on the newreading range. The RFID reader may then be moved to the newly determinedread points to provide substantially 100% coverage of the predefinedarea. The greater flexibility of movement of the RFID reader also allowsfor variations in storage conditions and/or RFID tag location densities.For example, if a particular region of a zone contains a source ofinterference or a greater number of RFID tags, the RFID reader may bepaused at that particular region for a longer duration of time to ensurethat all the RFID tags are read.

With particular reference now to FIG. 1, there is shown a simplifieddiagram of an RFID system 100 for moving a reader 106 within a zone 101,according to an embodiment. Although particular reference has been madeherein below to the RFID system 100 as including particular features, itshould be understood that the RFID system 100 may include additionalcomponents and that some of the components described may be removedand/or modified without departing from a scope of the RFID system 100.

The RFID system 100 is illustrated as including guide tracks 102 a and102 b, a channel 104 attached to the guide tracks 102 a and 102 b, and areader 106 attached to the channel 104. The guide tracks 102 a and 102 bmay be any reasonably suitable mechanical device for allowing thechannel 104 to move along the guide tracks 102 a and 102 b in thedirections indicated by the sets of arrows adjacent to each of the guidetracks 102 a and 102 b. For example, the guide tracks 102 a and 102 bmay comprise rails, wheels, ball bearings, magnets, etc., to which thechannel 104 may be movably attached. Moreover, as FIG. 1 shows, theguide tracks 102 a and 102 b may have a series of graduated markings atpredetermined intervals along the length of one or more of the guidetracks 102 a or 102 b. For example, there may be a marking at every inchor centimeter of one or more of the guide tracks 102 a and 102 b. Themarkings may be used in determining the precise position of the channel104 along the guide tracks 102 a and 102 b. While the graduated markingson the guide tracks 102 a and 102 b are shown as being diagonallyarranged in FIG. 1, a person having ordinary skill in the art willappreciate that the graduated markings may be horizontal or at any otherreasonably suitable angle.

The reader 106 may comprise any reasonably suitable device operable toread RFID tags. Although the reader 106 is shown as a simple blockdiagram in FIG. 1, a person having ordinary skill in the art willappreciate that the reader 106 may include additional components, suchas one or more antennas, an internal power source, memory, equipment tocommunicate with other electronic devices, etc. The reader 106 isoperable to move along the channel 104 in the directions indicated bythe arrows adjacent to the reader 106. For example, the channel 104 maycomprise a rail, wheels, magnets, ball bearings, etc., to which thereader 106 is movably attached. Like the guide tracks 102 a and 102 b,the channel 104 also comprises graduated markings to aid in determiningthe precise position of the reader 106 along the channel 104.

The guide tracks 102 a and 102 b generally define the zone 101 betweenthe guide tracks 102 a and 102 b, in which the reader 106 may be moved.That is, the reader 106 may be moved to different positions within thezone 101 to read RFID tags located within the zone 101. In addition, thereader 106 may be operable to read RFID tags located outside of the zone101. For instance, the reader 106 may be moved to a position near anedge of the zone 101 and the reading range of the reader 106 may extendbeyond the edge of the zone 101.

In one embodiment, FIG. 1 may be a birds-eye view of the RFID system100. That is, the zone 101 may be a predefined area, such as a room or awarehouse, and the guide tracks 102 a and 102 b may be attached to theceiling of the predefined area. Therefore, the channel 104 may movealong the guide tracks across the ceiling of the predefined area.However, in other embodiments, the guide tracks may be positioned on thefloor of the predefined area or mounted in any reasonably suitablelocation between the floor and ceiling of the predefined area. As such,the zone 101 may represent a three-dimensional area extending aboveand/or below the guide tracks 102 a and 102 b, channel 104, and reader106. In this regard, the reader 106 may be positioned to move verticallywith respect to the channel 104 to obtain data from RFID tags positionedat different heights. Also, the zone 101 may represent only a portion ofa predefined area and the reader 106 may be operable to read RFID tagslocated outside of the zone 101 and/or the predefined area may havemultiple zones and multiple RFID systems, as will be described ingreater detail below.

As mentioned above, it should be understood that the RFID system 100shown in FIG. 1 is merely an example of how such an RFID system 100 maybe configured. For example, it is within the level of ordinary skill inthe art to attach the reader 106 to the channel 104 in differentconfigurations. Therefore, in other embodiments, the reader 106 may siton top of the channel 104 or may be suspended underneath the channel104. In fact, the reader 106 may be lowered below the channel 104 orraised above the channel 104.

With particular reference now to FIG. 2, there is shown a simplifieddiagram of an RFID system 200 with a plurality of read points 202,according to an embodiment. Although particular reference has been madeherein below to the RFID system 200 as including particular features, itshould be understood that the RFID system 200 may include additionalcomponents and that some of the components described may be removedand/or modified without departing from a scope of the RFID system 200.

The RFID system 200 is illustrated as including a plurality of readpoints 202, which are represented here as a plurality of circles. Theread points 202 are optimum positions at which a reader, such as thereader 106, described above with respect to FIG. 1, may pause to scanfor RFID tags. By determining optimized read points, a reader may obtainfull blanket coverage of a predefined area. For example, the pluralityof read points 202 shown in FIG. 2, allow for full coverage of zone 206,as well as limited coverage of regions beyond the zone 206. The readpoints 202 may be determined by tessellating or dividing the predefinedarea into a plurality of hexagonal areas 204. For example, the readpoints 202 may be determined by tessellating the predefined area suchthat the predefined area fully or partially covers the least number ofhexagonal areas 204 in the tessellation pattern. Each of the hexagonalareas 204 may represent a reading range of a single reader 106.Therefore, the centers of each of the hexagonal areas 204 correspond toread points 202 where the reader 106 may pause to scan for RFID tags.

With respect to FIG. 3, there is shown a hexagonal area 300, accordingto an embodiment. For example, the hexagonal area 300, shown in FIG. 3may represent one or more of the hexagonal areas 204 depicted in FIG. 2.The center C of the hexagonal area 300 may be a read point for an RFIDreader. In this embodiment, the circle surrounding the hexagonal area300 represents the circular reading range 302 of the RFID reader. Thecircular reading range 302 has a radius r, with the RFID reader at thecenter C of the hexagonal area 300. As can be seen from FIG. 3, thelength from the center C to any vertex 304 of the hexagonal area 300 isr. Accordingly, the length of any sides of the hexagonal area 300 isalso r.

With respect to FIG. 4 there is shown a tessellated combined area 400and a predefined area 402, according to an embodiment. The predefinedarea 402 may represent the total area of a region where RFID tags areexpected to be located. For example, the predefined area 402 may be awarehouse or a portion of a warehouse in which RFID tags are expected tobe located. As described above, the hexagonal areas 204 may be arrangedtogether as a honeycomb of hexagonal areas 204 to form the combined area400. As such, there are no gaps between any two of the hexagonal areas204 in the combined area 400. The formation of the combined area 400 byarranging the hexagonal areas 204 together should stop only when thecombined area 400 is sufficient to cover or is larger than thepredefined area 402. The number of hexagonal areas 204 needed to formthe combined area 400 which is equal to or larger than the predefinedarea 402 depends on the reading range r of the RFID reader used in theRFID system. The larger the reading range 302, the fewer the number ofhexagonal areas 204 are needed to form the combined area 400.

With respect to FIGS. 5A and 5B, there are shown possible alignments ofthe predefined area 402 within the combined area 400, according to twodifferent embodiments. In fact, there are many possible ways of aligningthe predefined area 402 within the combined area 400. For example, abrute force approach of positioning one of the hexagonal areas 204 at acorner of the predefined area 402 as a reference hexagon may be used.Further possible alignments may be obtained by rotating a referencehexagon by a certain angle.

A method for determining an optimized alignment of the predefined area402 with the combined area 400 will be described as an embodiment. Inthis embodiment, the predefined area 402 is a rectangular area. However,a person having ordinary skill in the art will appreciate that in otherembodiments the predefined area 402 may be any other reasonably suitableshape. Referring back to FIG. 4, the rectangular predefined area 402 isarranged within the combined area 400 such that a vertex 410 of thepredefined area 402 coincides with a vertex 420 of one of the hexagonalareas 204, and an edge 411 of the predefined area 402 adjoining thevertex 410 coincides with an edge 421 of the hexagonal area adjoiningthe vertex 420. Since the predefined area 402 has two possibleorientations using the starting point shown in FIG. 4, this results intwo possible alignments as shown in FIG. 5A and FIG. 5B.

It should be noted that each of the two possible alignments shown inFIG. 5A and FIG. 5B allows only one degree of movement along thedirection of the coinciding edges 411 and 421. The aligned predefinedarea 402 is only allowed to move along the direction of the coincidingedges 411 and 412 until it touches the vertex of an end hexagonal areawhich is covered by the predefined area 402. With respect to FIG. 6,there is shown an example of the aligned predefined area 402 in FIG. 5Abeing moved along the direction of the coinciding edges 411 and 421until it touches the vertex of the end hexagonal area.

The alignment having the fewest number of the hexagonal areas 204 whichare either fully or partially covered by the predefined area 402corresponds to the optimized alignment of the predefined area 402 withthe combined area 400. The calculation of the number of the hexagonalareas 204 fully or partially covered by the predefined area 402 will nowbe described with reference to FIG. 7 and FIG. 8.

FIG. 7 shows a predefined area 402 being aligned on a combined area 400.The predefined area 402 has a length m and a width n. The length of eachedge of the hexagonal areas 204 is r (which is also the length from thecenter to each vertex of the hexagonal areas 204). The number ofhexagonal areas 204 which are either fully or partially covered by thepredefined area 402 is:

Z=x*y+V _(additional)−δ.  Equation (1)

In Equation (1), Z is the number of the hexagonal area 204 covered bythe predefined area 402, x is the number of the hexagonal areas 204 inthe horizontal direction (see edge 411 of FIG. 4), y is the number ofthe hexagonal areas 204 in the vertical direction (see edge 412 of FIG.4), V_(additional) is the additional hexagonal area(s), and δ is acorrection factor for certain boundary conditions.

The length covered by the edge 411, shown in FIG. 4, of the predefinedarea 402 is an addition of r and 2r in alternates. Therefore, the numberof complete “r-2r” pairs is

$\left\lfloor \frac{m}{3r} \right\rfloor.$

Since each “r-2t” covers 2 of the hexagonal areas 204, the number ofhexagonal areas 204 in the complete “r-2e” pair is:

$\begin{matrix}{H_{complete} = {2{\left( \left\lfloor \frac{m}{3r} \right\rfloor \right).}}} & {{Equation}\mspace{14mu} (2)}\end{matrix}$

In Equation (2), H_(complete) is the number of the hexagonal areas 204in the complete “r-2r” pair.

The fractional “r-2r” pair, if any, at the end of the predefined area402 is

$\frac{m}{3r} = {\left\lfloor \frac{m}{3r} \right\rfloor.}$

Therefore, the number of “r” in the fractional “r-2r” pair is:

$\begin{matrix}{E_{fraction} = {3{\left( {\frac{m}{3r} - \left\lfloor \frac{m}{3r} \right\rfloor} \right).}}} & {{Equation}\mspace{14mu} (3)}\end{matrix}$

In Equation (3), E_(fraction), is the number of “r” in the fractional“r-2e” pair.

FIG. 8 shows an illustration of the number of hexagonal areas 204 thatare needed (H_(fraction)) for different values of E_(fraction) accordingto an embodiment. As can be seen from FIG. 8, when E_(fraction) isbetween 0 and 1, the number of hexagonal areas 204 needed to cover thefractional “r-2r” pair is 1. When E_(fraction) is more than 1 but equalbut less than 2.5, the number of the hexagonal areas 204 needed to coverthe fractional “r-2r” pair is 2. When E_(fraction) is more than 2.5 butless than 3, the number of the hexagonal areas 204 needed to cover thefractional “r-2r” pair is 3. The relationship between the number of thehexagonal areas 204 needed to cover the fractional “r-2r” pair andE_(fraction) can be summarized using the following equation:

$\begin{matrix}{H_{fraction} = \left\{ \begin{matrix}{1,} & {if} & {0 \leq E_{frac} \leq 1} \\{2,} & {if} & {1 < E_{frac} \leq 2.5} \\{3,} & {if} & {2.5 < E_{frac} < 3.}\end{matrix} \right.} & {{Equation}\mspace{14mu} (4)}\end{matrix}$

In Equation (4), H_(fraction) is the number of hexagonal areas 204needed to cover the fractional “r-2e” pair. Therefore, the total numberof hexagonal areas 204 covered by the predefined area 402 in thehorizontal direction x is:

x=H _(complete) +H _(fraction).  Equation (5)

The length covered by the edge 412, shown in FIG. 4, of the predefinedarea 402 is √{square root over (r)}r for each hexagonal area covered.Therefore, the number of the hexagonal areas 204 covered by thepredefined area 402 in the vertical direction y covered by thepredefined area 402 in the vertical direction y is:

$\begin{matrix}{y = {\frac{n}{\sqrt{3}r}.}} & {{Equation}\mspace{14mu} (6)}\end{matrix}$

In Equation (6), If

$\frac{n}{\sqrt{3}r} - y$

is greater than 0.5, then additional hexagonal areas may be added to thetotal number of hexagonal areas 204 covered by the predefined area 402.In other words, if √{square root over (3)}(y+0.5)r<n, then:

$\begin{matrix}{V_{additional} = {\left\lfloor \frac{x}{2} \right\rfloor.}} & {{Equation}\mspace{14mu} (7)}\end{matrix}$

In addition, two cases of boundary conditions may be considered. Thefirst case that may be considered occurs when:

1<E_(fraction)<1.5, and  Equation (8)

√{square root over (3)}(y−0.5)r<n<√{square root over (3)}(y)r.  Equation(9)

In this case the correction factor is:

$\begin{matrix}{\delta = \left\{ \begin{matrix}{1,} & {if} & {{\left( {n - {\sqrt{3}{r\left( {y - 0.5} \right)}}} \right) + {\left( {E_{fraction} - 1} \right)r}} \leq {\frac{\sqrt{3}r}{2}.}} \\{0,} & {if} & {otherwise}\end{matrix} \right.} & {{Equation}\mspace{14mu} (10)}\end{matrix}$

The second case that may be considered is when:

2.5<E_(fraction)<3, and  Equation (11)

√{square root over (3)}(y−1)r≦n≦√{square root over(3)}(y0.5)r.  Equation (12)

In this case the correction factor is:

$\begin{matrix}{\delta = \left\{ \begin{matrix}{1,} & {if} & {{\left( {n - {\sqrt{3}{r\left( {y - 1} \right)}}} \right) + {\left( {E_{fraction} - 2.5} \right)r}} \leq {\frac{\sqrt{3}r}{2}.}} \\{0,} & {if} & {otherwise}\end{matrix} \right.} & {{Equation}\mspace{14mu} (13)}\end{matrix}$

Combining Equations (10) and (13), the correction factor is determinedusing the following expression:

$\begin{matrix}{\delta = \left\{ \begin{matrix}{1,} & \begin{matrix}{{{{if}\mspace{14mu} \left( {n - {\sqrt{3}{r\left( {y - 0.5} \right)}}} \right)} + {\left( {E_{frac} - 1} \right)r}} \leq \frac{\sqrt{3}r}{2}} \\{{{{and}\mspace{14mu} 1} < E_{fraction} < {1.5\mspace{14mu} {and}}}\mspace{14mu}} \\{{\sqrt{3}\left( {y - 0.5} \right)r} < n < {\sqrt{3}(y){r.}}}\end{matrix} \\{1,} & \begin{matrix}{{{{if}\mspace{14mu} \left( {n - {\sqrt{3}{r\left( {y - 1} \right)}}} \right)} + {\left( {E_{frac} - 2.5} \right)r}} \leq \frac{\sqrt{3}r}{2}} \\{{{{and}\mspace{14mu} 2.5} < E_{fraction} < {3\mspace{14mu} {and}}}\mspace{14mu}} \\{{\sqrt{3}\left( {y - 1} \right)r} < n < {\sqrt{3}\left( {y\; 0.5} \right)r}}\end{matrix} \\{0,} & {{otherwise}.}\end{matrix} \right.} & {{Equation}\mspace{14mu} (14)}\end{matrix}$

Combining Equations (1), (2), (4), (5) and (6), the total number ofhexagonal areas covered by the predefined area 402 is:

$\begin{matrix}{Z = {{\left\lbrack {{2\left( \left\lfloor \frac{m}{3r} \right\rfloor \right)} + H_{fraction}} \right\rbrack*\left\lceil \frac{n}{\sqrt{3}r} \right\rceil} + V_{additional} - {\delta.}}} & {{Equation}\mspace{14mu} (15)}\end{matrix}$

In Equation (15), V_(additional) is determined using Equation (7) and δis determined using Equation (14). The alignment of the predefined area402 with the combined area 400 which covers the fewest number ofhexagonal areas (that is, the lowest value of Z) is the optimizedalignment of the predefined area 402 with the combined area 400.

Using the optimized alignment of the predefined area 402 with thecombined area 400 determined as described above, the hexagonal areas204, which are fully or partially covered by the predefined area 402 maybe determined, for example, by physically marking the hexagonal areas204. The center of each of the hexagonal areas 204 determined to befully or partially covered by the predefined area 402 corresponds to aread point 202. In an embodiment, one or more static RFID readers may beplaced within the predefined area 402 at each of the determined readpoints 202. Accordingly, a full coverage of the predefined area 402 bythe RFID readers is achieved.

In an alternative embodiment, or in addition to the use of static RFIDreaders, one or more mobile RFID readers, such as the reader 106, shownin FIG. 1, may be used. For example, the guide tracks 102 a and 102 bmay be placed on either side of the predefined area 402, such that thepredefined area 402 is equivalent to the zone 101 or 206. Therefore, thechannel 104 may be moved across the predefined area 402 along the guidetracks 102 a and 102 b and the reader 106 may be moved along the channel104 to position the reader 106 at one or more of the read points 202.The reader 106 may also be raised or lowered to an optimum position inthe vertical or Z-axis. The size and number of zones, such as the zones101 or 206, will depend on the dimensions of the predefined area 402,tag volume, tag density, reader capacity and range, as well as themaximum length of the channel 104. However, as mentioned above, whilethe zones may define travel boundaries of a reader, the zones do notnecessarily demarcate a closed reading area because a reader 106 mayread tags outside of the zone in which the reader 106 is located and/orin adjacent zones also.

In one embodiment, the reader 106 may be moved along a predefined pathto each of the read points 202 to read RFID information from RFID tagslocated anywhere in the predefined area 402. For example, a predefinedpath of the reader 106 may involve passing the reader 106 through allthe read points 202 (FIG. 2). In other embodiments, however, thepredefined path may include only a portion of the read points 202. Forinstance, the predefined area 402 may be a warehouse having unused orotherwise unavailable portions. In such a case, the predefined path mayomit the read points 202 associated with the unused or unavailableportions of the predefined area 402. The reader 106 may be moved throughthe predetermined path and paused at each of the read points 202. As setforth above, pausing the reader 106 may include stopping the reader foruniform or varied durations of time at each of the read points 202.While paused at the read points 202, the reader 106 may scan for RFIDtags and read any information from any RFID tags within its readingrange.

Scanning for RFID tags may include transmitting an RF signal. The RFsignal may activate passive RFID tags, which transmit a respondingsignal. Alternatively, or in addition thereto, scanning may includesimply “listening for” and reading RF signals transmitted by RFID tagspowered from a source other than the RFID reader. In any event,information from RFID tags in the predefined area may be obtained,stored, and/or passed to another device.

After the reader 106 has stopped at one of the read points 202, thereader 106 may be moved to a next read point 202 along the predeterminedpath. At the next read point 202, the reader 106 may also pause and scanfor RFID tags before proceeding to another read point 202, until thereader 202 reaches the end of the predefined path. Thereafter, thereader 106 may return to the start point of the predefined path torepeat the process, reverse its direction along the predefined path, orbegin moving along a different path.

By moving the reader 106 to multiple read points 202 instead ofdedicating a static reader to every determined read point, possibleinterference between adjacent readers is avoided or greatly reduced.This greatly increases the reliability and efficiency of the RFIDsystem.

Turning again to FIG. 2, the number pairs inside of the circlesrepresenting the read points 202 indicate relative coordinates oridentifiers of each of the read points 202. The first number of thenumber pairs represents a position in the X dimension while the secondnumber in the number pairs represents a position in the Y dimension. Inthis manner, the read points 202 may be identified by their locations inrelation to each other. Although only the X and Y coordinates are shownin FIG. 2, it should be understood that the Z coordinate may also bedetermined and utilized. For example, if the guide tracks 102 a and 102b, described above with respect to FIG. 1, are mounted to a ceiling orotherwise above the floor, of a predefined area the reader 106 may bedynamically suspended from the channel 104 such that the reader 106 isoperable to be raised and lowered therefrom. In such a case, the Zcoordinate may be used to determine the optimal height at which thereader 106 should be positioned in the predefined area 402 to scan forRFID tags. In such a 3-dimensional case, hexagonal cylinders instead ofhexagonal areas 204 are used to determine the 3-dimensional locationsfor positioning the reader 106. The coordinates of the locations forplacing the RFID readers would be represented as (x_(r) y_(r) z_(r)),where z_(r) is the z-coordinate.

The absolute locations of the read points 202 may also be calculated.That is, the physical locations within the predefined area 402 of thecenter of each of the hexagonal areas 204 may be determined. Forexample, if the predefined area 402 is a warehouse or other building, itmay be determined how many meters, centimeters, feet, inches, etc., thevarious read points 202 are from various known positions, such as acorner of the predefined area 402 or a wall of the predefined area 402.In one embodiment, the absolute coordinates may be determined bydesignating the top left corner, as shown in FIG. 2, of the zone 206 asthe origin, or (0, 0, 0). If the relative coordinates are x_(r), y_(r),z_(r)=0, the absolute coordinates X_(abs), Y_(abs), and Z_(abs) of thecenter of the hexagonal areas 204 from the top-left corner may becalculated using the following equations, where “r” is the radius of theread range of the reader 106:

$\begin{matrix}{{X_{abs} = \frac{r\left( {{3x_{i}} - 2} \right)}{2}},} & {{Equation}\mspace{14mu} (16)}\end{matrix}$

$\begin{matrix}{{Y_{abs} = \frac{\sqrt{3}{r\left( {{2y_{i}} - 1} \right)}}{2}},} & {{Equation}\mspace{14mu} (17)}\end{matrix}$

if x_(i) is an odd number, and

Y_(abs)√{square root over (3)}r (y_(i)−1), if x, is an evennumber.  Equation (18)

Due to variations in the range of various readers and changingconditions inside the predefined area that affect readers, such as,environmental conditions, the absolute coordinates of the read points202 may vary in different predefined areas, which have substantiallysimilar dimensions. For example, two rectangular warehouses having thesame length, width, and height, may require different read points 202even when identical readers are used. The number of read points 202 ineach direction will also depend on the actual dimensions of thepredefined area 402, of course. Therefore, a map table of the readpoints 202 may be maintained to properly guide and position the reader106 inside the zone 101 or 206. For example, the map table may includethe number of each of the read points 202 and the relative and absolutecoordinates of each of the read points 202, as shown below:

Read Point #s Relative Coordinates Absolute Coordinates 1 (1, 1) (100,100) 2 (1, 2) (100, 200) 3 (2, 1) (250, 150) 4 (2, 1) (400, 250) 5 . . .. . .

The map table shown above is just one possible example of a map table,which may be utilized with the systems and methods described herein. Themap table shown above includes the number of each of the read points202, which may be indicative of the order in which the reader 106 ismoved in a predefined path or may simply be a random designation of theread points 202. The map table includes relative coordinates, which maybe substantially similar to the relative coordinates shown within thecircles of FIG. 2. The map table also includes the absolute coordinatesof each of the read points 202, which may be determined using themethods described above. The map table might be stored within a readercontroller application or may be stored in the reader 106, itself, aswill be described in greater detail below.

As mentioned above, the map table may be used to guide and position thereader 106 at the correct read points 202. For instance, when the reader106 is required to move from point 2 to 3, the reader 106 may beprovided with the relative coordinates as part of a movementinstruction. The map table may be referenced to correlate the relativecoordinates to the absolute coordinates so that it is known how manyinches, centimeters, etc, the reader 106 must move. The use of the maptable may aid in insulating various RFID system applications from thedetails of specific implementation and idiosyncrasies arising out ofdifferences in reader specifications.

However, in other embodiments, the reader 106 may simply be given themovement instructions in terms of absolute movements, such as 150 inchesin X direction and −50 inches in Y direction. In other examples, complexmovements, such as a move from point 1 to 4, may require the reader totraverse through a number of intermediate points and will benefit fromthe use route optimization algorithms. Standard algorithms from graphtheory and combinatorial optimization disciplines can be used for routeoptimization. For example, shortest path (for instance, Dijkstra'sAlgorithm) algorithms, minimum spanning trees algorithms, minimum weightspanning tree (for instance, Kruskal's Algorithm) algorithms, TravelingSalesman Problem algorithms, heuristics based solutions, etc., may beused. It should be noted that which algorithm to be used depends on theproblem, environment and any available data.

It is also possible to sub-divide the predefined area 402 intosub-areas. For instance, with respect to FIG. 9, there is shown an RFIDsystem 900 having multiple zones, according to an embodiment. The RFIDsystem 900 includes a first zone 902 and a second zone 904. Thepredefined area and, thus, each of the zones 902 and 904 has beentessellated according to the techniques described above and, thus, has aplurality of read points 906.

The boundaries of the zones 902 and 904 are defined by a pair of guidetracks 908 a and 908 b mounted on opposite boundaries of the zones 902and 904, respectively. Each of the zones 902 and 904 further includes achannel 910 a and 910 b movably attached between each set of the guidetracks 908 a and 908 b, respectively. Each of the zones 902 and 904 alsoincludes a mobile reader 912 a and 912 b movably attached to thechannels 910 a and 910 b, respectively. Therefore, each of the zones 902and 904 may be substantially similar to the zone 101, described abovewith respect to FIG. 1. In this manner the mobile readers 912 a and 912b may be moved to virtually any point within the zones 902 and 904,respectively.

While two different zones 902 and 904 are shown in FIG. 9, a personhaving ordinary skill in the art will appreciate that a predefined areamay be split into any reasonably suitable number of zones. Similarly,each of the zones 902 and 904 may have one dedicated mobile reader 912 aor 912 b to move to each of the read points 906 in each respective zoneor, in other embodiments, each of zones 902 and 904 may contain multiplereaders, both static and mobile.

The mobile readers 912 a and 912 b may each be moved along predefinedpaths within their respective zones to scan for RFID tags, such that allRFID tags within each of the zones 902 and 904 are read. In addition,RFID tags located outside of the zones 902 and 904 may also be read. Forexample, the mobile readers 912 a and 912 b may be moved to the readpoints 906 on the inner boundaries of each of the zones 902 and 904,respectively to read RFID tags located outside of the zones 902 and 904,because the reading range of the mobile readers 912 a and 912 b extendsto each vertex of the tessellated areas. Thus, the predefined area ismonitored efficiently because RFID tags located outside of the zones 902and 904 in areas, such as between the zones 902 and 904, may be readwithout having to physically move a reader into this area.

Moreover, the movement of the mobile readers 912 a and 912 b within eachof the zones 902 and 904 may be coordinated such that the two mobilereaders 912 a and 912 b do not come within close enough physicalproximity to interfere with each other. For example, the mobile reader912 a may be moved to the middle or left side of the zone 902 while themobile reader 912 b is moved to the left side of the zone 904. In thismanner, the movement of the mobile readers 912 a and 912 b is controlledsuch that the mobile readers 912 a and 912 b are not physically withineach others reading range at the same time.

However, in other embodiments, both of the mobile readers 912 a and 912b may be positioned in close enough proximity to each other that theirrespective reading ranges overlap. To avoid interference in thissituation, the scan timing of each of the mobile readers 912 a and 912 bmay be coordinated, such that only one of the mobile readers 912 a and912 b is actively scanning at a particular moment in time. In thismanner, interference between the two mobile readers 912 a and 912 b isreduced or eliminated because both of the readers 912 a and 912 b arenot actively scanning at the same time.

The location of the guide tracks 908 a and 908 b and, thus, theboundaries of the zones 902 and 904 may be very close to the derivedread points 906. In fact, the placement of the guide tracks 908 a and908 b shown in FIG. 9 is substantially in line with various read points906. This provides the maximum read point coverage to a channel andreader combination. However, in other embodiments the boundary of thezones 902 and 904 may not be close to any of the read points 906,because the guide tracks 908 a and 908 b are relatively fixed while theread points 906 are dependant on the reader range. Therefore, if theread range of a reader changes, the read points 906 may also change. Thelocation of the guide tracks 908 a and 908 b is described as relativelyfixed because the guide tracks 908 a and 908 b may be bolted, glued, orotherwise fastened at a particular location. Therefore, while it ispossible to detach, move, and re-attach the guide tracks 908 a and 908 bdoing so may require manual labor as opposed to the automated movementof the channels 912 a and 912 b along the guide tracks 908 a and 908 band the readers 912 a and 912 b along the channels 912 a and 912 b,respectively.

With respect to FIG. 10, there is shown a non-rectangular predefinedarea 1001. For example, the predefined area 1001 may represent awarehouse or other storage location having any reasonably suitablepolygonal shape. Optimized read points within the predefined area 1001may be determined by creating a minimum area enclosing rectangle (MAER)1002 around the predefined area 1001. The MAER 1001 may be determinedusing existing techniques, such as the rotating calipers algorithm.Optimized read points within the predefined area 1001 for pausing anRFID reader and scanning for RFID tags may be determined according tothe methods as described in the above embodiments.

With respect to FIG. 11, there is shown a block diagram of a locationoptimizing unit for determining optimized read points in a predefinedarea, according to an embodiment. The location optimizing unit 1101includes a hexagon field generator 1102, a rectangular area generator1103, a MAER calculator 1106, an alignment optimizer 1104, and a hexagoncenter locator 1105. The hexagon field generator 1102 receives thereading range of a reader as input and generates the combined area whichis comprised of the honeycomb of hexagonal areas. As previouslydescribed, each hexagonal area represents the circular reading range ofthe reader, and the length of each side of the hexagonal areas is equalto the radius r of the circular reading range. The rectangular areagenerator 1103 receives the dimensions of the predefined area, forexample a warehouse, as input and generates a rectangular arearepresenting the predefined area or the warehouse. In the case where thepredefined area is a non-rectangular shape, the rectangular areagenerator 1103 passes the dimensions of the predefined area to the MAERcalculator 1106 to determine the smallest rectangle that encloses thepredefined area. The MAER calculator 1106 returns the dimensions of thesmallest rectangle to the rectangular area generator 1103.

The alignment optimizer 1104 receives the combined area from the hexagonfield generator 1102 and the rectangular area from the rectangular areagenerator 1103 as inputs and determines an optimized alignment of therectangular area with the combined area in such a way that therectangular area totally or partially covers a minimum number ofhexagonal areas. The optimized alignment may be generated according tothe method described above. The alignment optimizer 1104 generates asoutput a combined hexagonal field (represented by the hexagonal areastotally or partially covered by the predefined area) covering thepredefined area or the warehouse.

The hexagon center locator 1105 receives the combined hexagonal fieldfrom the alignment optimizer 1104 as input, and determines a list ofcoordinates of the center of each of the hexagonal area of the combinedhexagonal field. The list of coordinates corresponds to the locationsfor putting a RFID reader in order to obtain a full coverage of thepredefined area.

In an embodiment, the alignment optimizer 1104 includes a rectangle onhexagon aligner 1107, a hexagon counter 1108 and a comparator 1109. Therectangle on hexagon aligner 1107 receives the combined area and therectangular area, and aligns the rectangular area on the combined areain all possible ways in order to generate the most optimized alignment.

For each alignment generated by the rectangle on hexagon aligner 1107,the hexagon counter 1108 calculates the number of hexagonal areas of thecombined area that are fully or partially covered by the predefinedarea. The number of hexagonal areas may be calculated using equation(15) described above.

The comparator 1109 compares the number of hexagonal areas of thevarious alignments and identifies the alignment which requires theminimum number of hexagonal areas. The alignment requiring the minimumnumber of hexagonal areas is the optimized alignment of the rectangulararea with the combined area as determined by the alignment optimizer1104.

With respect to FIG. 12, there is shown an RFID system 1200, accordingto another embodiment. Although particular reference has been madeherein below to the RFID system 1200 as including particular features,it should be understood that the RFID system 1200 may include additionalcomponents and that some of the components described may be removedand/or modified without departing from a scope of the RFID system 1200.

The RFID system 1200 includes a pair of guide tracks 1202, a channel1204, and a reader 1206. These components may be substantially similarto the complimentary components described above with respect to FIG. 1and FIG. 9. The RFID system 1200 includes four different zones A-D,between the guide tracks 1202. Therefore, the channel 1204 may movealong the guide tracks 1202 through each of the zones A-D and the reader1206 may move along the channel 1204 to different positions within thezones A-D. Although not shown in FIG. 12, the zones A-D may betessellated and read points within the zones A-D may be determinedaccording to the embodiments described above. Therefore, the reader 1206may move through and pause at different positions within the zones A-Dto read RFID tags.

In order to accurately determine the location of the reader 1206 and toprecisely control the movement of the reader 1206 to specific positions,the RFID system 1200, according the embodiment shown in FIG. 12,includes range markers 1208 a-1208 d. The range markers 1208 a-1208 dcomprise devices, which allow the location of the channel 1204 and thereader 1206 to be determined. For example, the range markers 1208 a-1208d may include sensors and/or transponders, which communicate with eachother and with the reader 1206. In one embodiment, one or more of therange markers 1208 a-1208 d may include a GPS device to determineposition information or may be pre-programmed with position information.As such, the range markers 1208 a-1208 d may also serve the purpose ofdefining the dimensions of one or more of the zones A-D and/or theentire predefined area. The reader 1206 and one or more of the markers1208 a-1208 d may transmit signals there between to determine thedistance from the reader 1206 to one or more of the markers 1208 a-1208d. In this manner, the position of the reader 1206 between the markers1208 a-1208 d may be determined with a relatively high degree ofaccuracy.

Alternatively, or in addition thereto, the precise control of themovement and position of the channel 1204 and/or the reader 1206 mayalso be achieved in other ways. For instance, precision stepper motorsoperable to calculate and precisely control the direction and degree ofmovement may be deployed to control the movement of the reader 1206and/or the channel 1204. In this manner, the motor itself may keep trackof the precise distance that the motor has moved the channel 1204 or thereader 1206.

Positional Identifiers on the guide tracks 1202 and/or the channel 1204may also be used. Positional identifiers include the graduated markingsdescribed above with respect to FIG. 1. Positional identifiers alsoinclude electronic markers that may be identified by sensors on thechannel 1204 and/or the reader 1206. In an embodiment, positionalidentifiers may include equidistant grooves in the guide tracks 1202and/or the channel 1204 where gears used to move the channel 1204 or thereader 1206 will mesh with the grooves during movement. These positionalidentifiers serve as a channel position and movement guides.

Movement may also be controlled using inertial navigation sensors, whichare sensors that determine direction and amount of motion along eachaxis of movement. Inertial navigation sensors may continuously check andcontrol the motion of the channel 1204 and/or the reader 1206.

With respect to FIG. 13, there is shown a reader manager 1300, accordingto another embodiment. Although particular reference has been madeherein below to the reader manager 1300 as including particularfeatures, it should be understood that the reader manager 1300 mayinclude additional components and that some of the components describedmay be removed and/or modified without departing from a scope of thereader manager 1300.

The reader manager 1300 may be configured to control the movement of areader, such as the readers 106 and 1206, described above with respectto FIGS. 1 and 12, respectively. The reader manager 1300 may be anintegrated component of a reader or may be a separate component notphysically associated with a reader, as will be described in greaterdetail below. The reader manager 1300 includes an area marker module1302, a layout marker module 1304, an obstacle position identifier 1306,and a range and speed calibration module 1308, each of which maycomprise hardware, software, firmware, or a combination thereof. Thearea marker module 1302 may receive data collected by the range markers1208 a-1208 d, described above with respect to FIG. 12. In one example,one or more of the range markers 1208 a-1208 d may collect informationfrom the other range markers 1208 a-1208 d and wirelessly transmit thecollected information to the area marker module 1302. For example, thearea marker 1302 may receive the relative or absolute coordinates of oneor more of the range markers 1208 a-1208 d. This data may be used todetermine the position of the reader in relation to the range markers1208 a-1208 d.

The layout module 1304 may contain information regarding the dimensionsof the predefined area in which the reader is configured to move. Forexample, the layout module 1304 may either be pre-programmed with dataregarding the shape and dimensions of one or more zones or may utilizethe data received from the area marker module 1302 to determine theshape and dimensions of the predefined area. The obstacle positionidentifier 1306 may contain data regarding obstacles in the predefinedarea that the reader must navigate around. For instance, a reader may besuspended from a ceiling of a warehouse and may have to navigate aroundducts or other HVAC equipment mounted to the ceiling. Data aboutobstacles may be pre-programmed into the obstacle position identifier1306 or the obstacle position identifier 1306 may store the coordinatesof obstacles as they are encountered by a reader in real-time.

The range and speed calibration module 1308 monitors the distance andspeed at which the reader moves. When a determination is made that thereader needs to move to a read point, the range and speed calibrationmodule 1308 determines the distance the reader must move to reach theread point and the time it will take the reader to move to the readpoint at a certain speed. The range and speed calibration module 1308monitors the readers movement to ensure the reader is moving at thecorrect speed for the correct duration of time.

With respect to FIG. 14, there is shown an RFID control system 1400,according to another embodiment. Although particular reference has beenmade herein below to the RFID control system 1400 as includingparticular features, it should be understood that the RFID controlsystem 1400 may include additional components and that some of thecomponents described may be removed and/or modified without departingfrom a scope of the RFID control system 1400.

The RFID control system 1400 shows various components, which may be usedto determine read points and control the movement of a reader through apredefined area to scan for RFID tags at the read points. The componentsshown in the RFID control system 1400 may be integrated into a reader orsome or all of the components may be physically independent from thereader. For example, one or more of the components shown in the RFIDcontrol system 1400 may be part of a computer system located within thepredefined area or at a remote monitoring location. In one embodiment, acentral monitoring station may monitor multiple predefined areas each ofwhich has an RFID tracking system.

The RFID control system 1400 includes a reader manager 1412, which maybe substantially similar to the reader manager 1300, described abovewith respect to FIG. 13. Thus, the reader manager 1412 may be a centralmodule designed to govern the movement of one or more readers in apredefined area, such as a warehouse. The reader manager 1412 mayinteract with all the other modules in the RFID control system 1400.When the reader manager 1412 receives a read command, the reader manager1412 may position the appropriate reader at the appropriate read pointto scan for RFID tags.

A read point optimizer 1402 may act as the brain of the RFID controlsystem 1400. For instance, the read point optimizer 1402 may collect andevaluate data from the area marker module 1302, the obstacle positionidentifier 1306, and the range and speed calibration module 1308. Theread point optimizer 1402 may identify the read point based on thereader range and the warehouse dimensions. In this manner, the readerdoes not need to be pre-programmed with the coordinates of the readpoints, because the read point optimizer 1402 may automaticallydetermine the read points by collecting the necessary information andutilizing the techniques described above. For example, in the case of anon-rectangular warehouse, the read point optimizer 1402 will performthe calculations based on a minimum area bounding rectangle. The readpoint optimizer 1402 may provide the relative and/or absolutecoordinates of the read points to the reader manager 1412.

A coordinate generator 1404 may receive relative coordinates anddetermine the absolute coordinates of the read points. For example, thecoordinate generator 1404 may access a map table to compare relativecoordinates to absolute coordinates for one or more read points. A zoneselector 1406 may receive the absolute coordinates and direct the readermanager 1412 to the appropriate zone controller. That is, a predefinedarea may be divided into a plurality of zones, where each zone has itsown dedicated zone controller 1408. Therefore, the zone selector 1406may determine in which zone the read point is located based on theabsolute coordinates of the read point.

A zone controller 1408 may receive the reader positioning details fromthe reader manager 1412. For example, the zone controller 1408 mayreceive the absolute coordinates of the next read point. The zonecontroller 1408 interacts with a channel controller 1410 and a readercontroller 1414. This allows for different channel and reader movementtechnologies to be deployed in different zones.

The channel controller 1410 controls the movement of a channel along apair of guide tracks. For example, the channel controller 1410 maycontrol the movement of the channel 104 or 1204 along the guide tracks102 a, 102 b or 1202, respectively. The channel controller 1410 mayreceive the channel movement details, such as the target location forpositioning the channel over the next read point, from the zonecontroller 1408. The channel controller 1410 may then move the channelto the target location. The channel controller 1410 includes a tracker1411 and a mover 1412. The tracker 1411 provides constant feedback onthe current location of the channel and the mover 1412 moves the channelbased on this feedback and the target location.

The reader controller 1414 controls the movement of a reader along achannel. For example, the reader controller 1414 may control themovement of the reader 106 or 1206 along the channel 104 or 1204,respectively. The reader controller 1414 receives the reader movementdetails, such as the target location for the reader from the zonecontroller 1408 and moves the reader to the target location. The readercontroller 1414 also includes a tracker 1415 and a mover 1416. Thetracker 1415 provides constant feedback on the current location of thereader and the mover 1416 moves the reader based on this feedback andthe target location.

Turning now to FIG. 15, there is shown a flow diagram of a method 1500for scanning for RFID tags, according to an embodiment. It is to beunderstood that the following description of the method 1500 is but onemanner of a variety of different manners in which an example of theinvention may be practiced. It should also be apparent to those ofordinary skill in the art that the method 1500 represents a generalizedillustration and that other steps may be added or existing steps may beremoved, modified or rearranged without departing from a scope of themethod 1500.

The description of the method 1500 is made with reference to theelements depicted in FIGS. 1-14, and thus makes reference to theelements cited therein. It should, however, be understood that themethod 1500 is not limited to the elements set forth in FIGS. 1-14.Instead, it should be understood that the method 1500 may be practicedby a system having a different configuration than that set forth inFIGS. 1-14.

The method 1500 may be initiated at step 1502, where a channel within atleast one zone is moved along guide tracks. The at least one zone may bea predefined area or any lesser portion thereof. For example, the atleast one zone may be substantially similar to the zone 101, the firstand second zones 902 and 904, or the zones A-D described above withrespect to FIGS. 1, 9, and 12, respectively. The predefined area may besubstantially similar to the predefined area 402. As such, thepredefined area may be a room or a building, such as a warehouse. Theguide tracks may be any mechanical devices configured to allow a channelto move thereon and, thus, may include wheels, rails, ball bearings,magnets, etc. In one embodiment, the guide tracks may be fixed to aceiling of the predefined area. Therefore, in this embodiment, the zonemay extend in three dimensions from the area between the guide tracks onthe ceiling, down underneath the guide tracks to a floor of thepredefined area. Similarly, in other embodiments, the zone may extend inthree dimensions either above and/or below the guide tracks.

At step 1504, a mobile RFID reader is moved along a channel. Like theguide tracks, the channel may also include any mechanical deviceconfigured to move along the guide tracks and allow the reader to movealong the channel. The mobile RFID reader may comprise any reasonablysuitable device configured to read RFID tags. By moving the channelalong the guide tracks and moving the mobile RFID reader along thechannel, the mobile RFID reader may be moved to virtually any pointwithin the at least one zone.

At step 1506, the mobile RFID reader is paused at a read point. Pausingmay include slowing the speed of the mobile RFID reader or bringing themobile RFID reader to a complete stop for a duration of time. The readpoint may be an optimized location for scanning for RFID tags and may bedetermined by the techniques described above. For example, a pluralityof hexagonal areas may be combined together to create a combined areasuch that no gaps or overlaps exist between the plurality of hexagonalareas. The combined area may be equal to or larger than the predefinedarea. Each of the hexagonal areas may have substantially the samedimensions and the distance between the center of each of the hexagonalareas and a vertex of each of the hexagonal areas may substantiallycorrespond to the reading range of the RFID reader. Therefore, thecenter of each of the hexagonal areas may substantially correspond to aread point.

At step 1508, the RFID reader may scan for RFID tags. Scanning for RFIDtags may include transmitting an RF signal. The RF signal may activatepassive RFID tags, which then transmit a responding signal.Alternatively, or in addition there, scanning may include simply“listening for” and reading RF signals transmitted by RFID tags poweredfrom a source other than the RFID reader. In any event, information fromRFID tags in the predefined area may be obtained, stored, and/or passedto another device.

Some or all of the operations set forth in the method 1500 may becontained as a utility, program, or subprogram, in any desired computeraccessible medium. In addition, the method 1500 may be embodied by acomputer program, which may exist in a variety of forms both active andinactive. For example, it can exist as software program(s) comprised ofprogram instructions in source code, object code, executable code orother formats. Any of the above can be embodied on a computer readablemedium, which include storage devices and signals, in compressed oruncompressed form.

Exemplary computer readable storage devices include conventionalcomputer system RAM, ROM, EPROM, EEPROM, and magnetic or optical disksor tapes. Exemplary computer readable signals, whether modulated using acarrier or not, are signals that a computer system hosting or runningthe computer program can be configured to access, including signalsdownloaded through the Internet or other networks. Concrete examples ofthe foregoing include distribution of the programs on a CD ROM or viaInternet download. In a sense, the Internet itself, as an abstractentity, is a computer readable medium. The same is true of computernetworks in general. It is therefore to be understood that anyelectronic device capable of executing the above-described functions mayperform those functions enumerated above.

The system and methods described herein address the challenges inachieving substantially 100% coverage of a predefined area, such as awarehouse, using mobile RFID readers. Data may be collected efficientlyby moving and pausing a reader at different optimized read points inorder to limit redundant reads of the same RFID tags. Determiningoptimized read points allows RFID tags located anywhere in thepredefined area to be read with the smallest possible set of readpoints. This makes the reading process very efficient and improvesreader utilization significantly. The dynamic movement of the readeralso provides flexibility of using readers with different read rangesand allows one reader to cover a large area. Moreover, the zoning of thepredefined areas allows for different configurations to be used indifferent areas based on changing circumstances, such as tag-densitiesand storage conditions. The methods and systems described herein allowfor continuous adaptive optimizations of a predefined area.

What has been described and illustrated herein is a preferred embodimentof the invention along with some of its variations. The terms,descriptions and figures used herein are set forth by way ofillustration only and are not meant as limitations. Those skilled in theart will recognize that many variations are possible within the spiritand scope of the invention, which is intended to be defined by thefollowing claims—and their equivalents—in which all terms are meant intheir broadest reasonable sense unless otherwise indicated.

1. An RFID system comprising: a pair of guide tracks located on opposite boundaries of at least one zone, wherein the at least one zone is at least a portion of a predefined area; a channel movably attached to the guide tracks, wherein the channel is configured to move along the guide tracks through the at least one zone; and a mobile RFID reader movably attached to the channel, wherein the mobile RFID reader is configured to move along the channel and pause at a plurality of read points within the at least one zone to scan for RFID tags located within the predefined area, wherein the plurality of read points are determined by an arrangement of a plurality of hexagonal areas which are grouped together to create a combined area, wherein the combined area is aligned with the predefined area to define locations of the plurality of hexagonal areas, and wherein substantially central locations of each hexagonal area represent the plurality of read points. (I am not sure whether the nexus between determining the read points and arranging hexagonal areas to create a combined area is clear)
 2. The RFID system of claim 1, wherein the predefined area is a warehouse, which is configured to stores items associated with the RFID tags and the guide tracks are attached to a ceiling of the warehouse.
 3. The RFID system of claim 1, wherein the plurality of read points are substantially optimized locations for reading RFID tags to obtain substantially complete coverage of the at least one zone while reducing an amount of redundant reads of the RFID tags.
 4. The RFID system of claim 1, wherein the combined area is equal to or larger than the predefined area.
 5. The RFID system of claim 4, wherein the hexagonal areas all have substantially the same dimensions and a distance from the center of each of the hexagonal areas to a vertex of each of the hexagonal areas substantially corresponds to a reading range of the RFID reader.
 6. The RFID system of claim 1, further comprising: a reader manager configured to facilitate the movement of the RFID reader between the plurality of read points, wherein the reader manager stores a map table containing both the relative and absolute coordinates of the plurality of read points.
 7. The RFID system of claim 1, wherein at least one of the plurality of read points coincides with the position of at least one of the pair of guide tracks such that the mobile RFID reader is operable to read RFID tags located outside of the boundaries of the at least one zone.
 8. The RFID system of claim 1, further comprising: at least one of an area marker module configured to determine the position of the mobile RFID reader within the predefined area, a layout module configured to determine dimensions of the at least one zone, an obstacle position identifier configured to store data regarding obstacles in the predefined area, and a range and speed calibration module configured to monitor the movement of the mobile RFID reader.
 9. The RFID system of claim 1, wherein the predefined area includes a second zone and, wherein the RFID system further comprises: a second mobile RFID reader configured to move through the second zone and pause at a plurality of read points within the second zone to read RFID tags located within the second zone.
 10. A method of scanning for RFID tags comprising: arranging a plurality of hexagonal areas together to form a combined area, wherein each hexagonal area represents an area of coverage of a mobile RFID reader; aligning the combined area with a predefined area to define locations of the plurality of hexagonal areas in the predefined area; moving a channel along a pair of guide tracks, wherein the guide tracks are located on opposite boundaries of at least one zone, wherein the at least one zone is at least a portion of the predefined area; moving the mobile RFID reader along the channel through at least a portion of the at least one zone; pausing the mobile RFID reader at a read point within the at least one zone, wherein the read point comprises a substantially central location of a hexagonal area; and scanning for RFID tags with the mobile RFID reader while the mobile RFID reader is paused at the read point.
 11. The method of claim 10, wherein moving a channel along a pair of guide tracks comprises transmitting channel movement details from a zone controller to a channel controller, moving the mobile RFID reader along the channel comprises transmitting reader movement details from a zone controller to a reader controller, and scanning for RFID tags comprises reading information from RFID tags located within the predefined area.
 12. The method of claim 10, further comprising: determining the position of the mobile RFID reader within the predefined area to monitor the movement of the mobile RFID read with respect to the predefined area.
 13. The method of claim 10, wherein the hexagonal areas all have substantially the same dimensions and a distance from the center of each of the hexagonal areas to a vertex of each of the hexagonal areas substantially corresponds to a reading range of the RFID reader.
 14. The method of claim 10, wherein the guide tracks are attached to the ceiling of a warehouse and scanning for RFID tags comprises scanning for RFID tags located underneath the ceiling of the warehouse.
 15. The method of claim 10, wherein the at least one zone includes a plurality of read points and the method further comprises: moving the mobile RFID reader to another one of the plurality of read points; pausing the mobile RFID reader at the another one of the plurality of read points; and scanning for RFID tags at the another one of the plurality of read points.
 16. The method of claim 10, wherein pausing the mobile RFID reader comprises stopping the mobile RFID reader at the read point for a duration of time while the mobile RFID reader scans for RFID tags.
 17. The method of claim 10, further comprising: determining the relative and absolute coordinates of the read point; and storing the relative and absolute coordinates in a map table.
 18. The method of claim 10, wherein the predefined area includes a second zone having a second mobile RFID reader and the method further comprises: moving the second mobile RFID reader through the second zone such that a reading range of the second mobile RFID reader is not within a reading range of the mobile RFID reader.
 19. A computer readable storage medium on which is embedded one or more computer programs, said one or more computer programs implementing a method for localizing a tag, said one or more computer programs comprising a set of instructions for: arranging a plurality of hexagonal areas together to form a combined area, wherein each hexagonal area represents an area of coverage of a mobile RFID reader; aligning the combined area with a predefined area to define locations of the plurality of hexagonal areas in the predefined area; moving a channel along guide tracks, wherein the guide tracks are located on opposite boundaries of at least one zone, wherein the at least one zone is at least a portion of the predefined area in the combined area; moving the mobile RFID reader along the channel through at least a portion of the at least one zone; pausing the mobile RFID reader at a read point within the at least one zone, wherein the read point comprises a substantially central location of a hexagonal area; and scanning for RFID tags with the mobile RFID reader while the mobile RFID reader is paused at the read point.
 20. The computer readable storage medium of claim 19, further comprising a set of instructions for: moving the mobile RFID reader to another one of the plurality of read points; pausing the mobile RFID reader at the another one of the plurality of read points; and scanning for RFID tags at the another one of the plurality of read points. 